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Small G proteins of the Rho family, which includes Rho, Rac and Cdc42,
regulate phosphorylation pathways that control a range of biological functions
including cytoskeleton formation and cell proliferation. Rho proteins act as
molecular switches, with an active GTP-bound form and an inactive GDP-bound
form. The inactive GDP bound form is promoted by GTPase-activating proteins
(GAPs). GAP proteins specific for Rho contain a conserved region of around 200
amino-acid residues, the Rho-GAP domain. This domain can accelerate the GTP
hydrolysis activity of Rho by five orders of magnitude . RhoGAP domains are
usually associated with other signaling modules like SH2 (see <PDOC50001>),
SH3 (see <PDOC50002>) or PH (see <PDOC50003>).
Like other GAP domains Rho-GAP is exclusively helical (nine helices) (see
<PDB:1RGP>) . The core of the domain forms a four-helix bundle. The most
conserved residues across the family are located on the bundle face that
interacts with the G protein . Rho-GAP domain like Ras-GAP supplies an
arginine residue in trans into the active site of the G protein which confers
a self-stimulatory GAP activity through homophilic interaction .
Some of the proteins containing a RhoGAP domain are listed below:
Mammalian ARAP 1,2 and 3 proteins, a family of GTPase activating proteins
that contains both a RhoGAP and a ARFGAP domains (see <PDOC50115>). They
can regulate Rho or ARF G proteins according to their localization in the
Vertebrate β-chimaerin protein, a GTPase activating protein for the Rho-
like GTPase Rac.
Mammalian Nadrin protein, a neuron-specific GTPase-activating protein
involved in regulated exocytosis.
Mammalian unconventional myosin-9b.
Mammalian breakpoint cluster region protein (BCR) and Drosophila Rotund
protein, GTPase-activating proteins for Rac and Cdc42.
Mammalian Rho-GAP hematopoietic protein C1.
Mammalian Rho-GTPase-activating protein 6. It promotes continuous
elongation of cytoplasmic processes during cell motility and simultaneous
retraction of the cell body changing the cell morphology.
Mammalian phosphatidylinositol 3-kinase regulatory α subunit, an
adapter subunit of the phosphatidylinositol 3-kinase (PI3K). It has a
critical role in signal transduction pathways originating from a variety of
Mammalian Inositol polyphosphate 5-phosphatase OCRL-1 (EC 3.1.3.-). It may
function in lysosomal membrane trafficking by regulating the specific pool
of phosphatidylinositol 4,5-bisphosphate that is associated with lysosomes.
Mammalian type II inositol-1,4,5-trisphosphate 5-phosphatase involved in
signal-terminating reaction (EC 188.8.131.52.).
Yeast LRG1 and SAC7 proteins, the two major Rho GTPase-activating proteins.
The SAC7 protein is involved in assembly of actin.
Yeast BEM2 protein, a GTPase activating protein involved in the control of
The profile we developed covers the whole domain.
January 2003 / First entry.
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